using samples in blender cycles render layer tab
As indicated by the tooltip when hovering the mouse pointer over it, the Render Layer Samples setting allows you to override the Number of samples used. Setting it to 0 (the default) tells Blender to use whatever is the default for the scene (ie, the number of samples set in the Samples panel of the Render properties). Setting it to a non-zero value will use that number of samples for that render layer.

Eg, setting it to ‘1’ will render that layer as if the Render Samples is set to 1.